We are applying autoradiographic techniques to the study of renal innervation in an effort to localize tritiated norepinephrine ultrastructurally in the renal sympathetic nerves and thus gain information on their precise relationships with renal structures. We are determining the grain distribution on the neural, vascular, and tubular components of the juxtaglomerular apparatus at the cellular and organelle level. We are also attempting, by combining histochemical with autoradiographic methods, to localize ultrastructurally norepinephrine and acetylcholinesterase in the same nerves and, therefore, elucidate the old question about the possible presense of that enzyme in adrenergic nerves. We are investigating the afferent (myelinated) innervation of the kidney and renal neural receptors using serial section light and electron microscopy. Our objective is to establish the location, structure, and morphologic relationship of the receptors with the tubular and vascular components of the kidney. The connection between the myelinated (afferent) and the unmyelinated, sympathetic (efferent) innervation of the kidney will be studied using autoradiographic methods. Based on anatomical studies we have proposed a "contact model" for the juxtaglomerular apparatus. This model, for which we have no direct experimental evidence, could explain, however, a great deal of the experimental information available. In this project, we want to provide experimental support for the model. By changing the rate of renin secretion by well established methods, we hope to be able to visualize correlative changes in the space separating the vascular and tubular components of the JGA. Studies in the whole animal and in the isolated perfused rat kidney model will be carried out.